Generally, laundry machines are classified into a vertical type laundry machine, a drum of which is mounted in a vertical direction, and a horizontal type laundry machine, the drum of which is mounted in a horizontal direction. A typical example of the vertical type laundry machine is a pulsator type washing machine, and a typical example of the horizontal type laundry machine is a drum type washing machine.
However, laundry machines do not merely refer to machines that are capable of washing laundry but may include a drying machine that is capable of drying the laundry.
In the drum type washing machine, as the drum is mounted in the horizontal direction as described above, laundry received in the drum is washed by a lifting and dropping operation.
FIGS. 1 and 2 schematically illustrate the structure of a conventional drum type washing machine.
As shown in the drawings, the drum type washing machine includes a machine body 10, a tub 20 mounted in the machine body 10, a drum 30 rotatably mounted in the tub 20, and a driving unit for driving the drum 30.
At the front part of the machine body 10 is formed a laundry inlet hole 11, through which laundry is put into the drum. A door 40 is mounted to the machine body adjacent to the laundry inlet hole 11 for opening and closing the laundry inlet hole.
At opposite sides of the bottom of the outer circumference of the tub 20 are mounted dampers 21, which support the tub 20 in the machine body 10.
In the lower part of the tub 20 is mounted a washing water heater 60 for heating washing water, by which the temperature of the washing water used to wash laundry can be controlled.
The drum 30 is rotatably mounted in the tub 20. At the circumference of the drum 30 are formed a plurality of through-holes 31, through which washing water is introduced into or discharged from the drum.
The driving unit includes a driving motor 71 for driving the drum 30, and a belt 72 for transmitting the driving force of the driving motor 71 to the drum 30.
In the conventional drum type washing machine with the above-stated construction, a washing operation, a rinsing operation, and a spin-drying operation is automatically carried out for a predetermined period of time according to a control signal from a controller (not shown) while laundry and a predetermined amount of detergent are received in the drum 30, whereby the laundry is washed.
In the above-described conventional drum type washing machine, however, the amount of washing water used to wash the laundry is excessive. As a result, a large amount of washing water and power is unnecessarily consumed.
Specifically, in the conventional drum type washing machine, contaminants are not separated from the laundry unless the laundry is submerged in the washing water for a long period of time. For this reason, a large amount of washing water is needed.
Furthermore, in the case of the conventional drum type washing machine, the washing water supplied into the tub is heated by the washing water heater, and then a laundry sterilizing process is carried out using the heated washing water. As a result, the power consumption is also unnecessarily large.
In recent years, there has been proposed a drum type washing machine having an additional steam supply unit mounted therein for supplying high-temperature steam into the drum, whereby the sterilization of the laundry is accomplished only using a small amount of washing water.
However, the conventional steam supply unit has the following problems since an amount of washing water necessary to generate steam is automatically supplied.
First, an additional water supply valve and an additional water supply channel are needed to supply water to the steam supply unit.
For this reason, the manufacturing costs of the conventional drum type washing machine are increased. Furthermore, the structure of the conventional drum type washing machine is complicated, and therefore, the manufacturing efficiency of the conventional drum type washing machine is lowered.
Secondly, in the case that the water supply valve malfunctions or in the case that a sensor for detecting the water level in the steam supply unit is out of order, the heat generation is performed although the water is not sufficiently supplied, which may lead to the occurrence of a fire.
This problem is caused because a user cannot recognize the amount of washing water supplied to the steam supply unit.
In addition, the conventional steam supply unit is constructed such that the steam is injected into the drum from the top part of the drum. As a result, when the amount of the injected steam is not sufficiently large or when the injection pressure of the steam is not sufficiently high, the steam cannot be smoothly supplied to the laundry placed at the bottom of the drum. Consequently, the washing efficiency using the steam is significantly lowered.
On the other hand, it is also possible to embody a drying machine having the steam supply unit in addition to the washing machine having the steam supply unit. This drying machine not only dries laundry but also supplies the steam to wrinkled dry laundry, thereby accomplishing sterilization of the laundry and removal of wrinkles from the laundry.
However, it is necessary that this drying machine be installed at the place where the drying machine is connected to an additional external water supply facility, in addition to the above-mentioned problems.
This is because water supply is not necessary for a general drying machine, and therefore, the general drying machine is usually installed at the place where only power supply to the general drying machine is possible. Consequently, in the case that an additional water supply facility is installed to supply water to the steam supply unit, the usefulness of the drying machine including the steam supply unit is lowered.